The exchangable cartridges intended to be used with the dispenser and to be connected with it, are generally known to be used for processing pasty or viscous substances, which are delivered through the cartridge opening by the action of the delivery plunger. A difficulty in working with cartridges of this nature consists in the fact that the contents tend to show afterflow after the action on the delivery plunger has ceased. This phenomenon is undesirable and a nuisance because it prevents clean work and makes dispensing of the exact measured amount impossible. The cause of this afterflow has been found to lie in the cartridge body's--most often manufactured as a thinwalled disposable plastic item--"breathing" upon dispensing, i.e. it elastically expands from the inside due to the pressure of the cartridge content when the plunger is advanced and assumes its original shape again when no more delivery pressure is applied. Moreover, the connection between cartridge and attachment is not completely rigid but rather is elastically deformed when the ram is advanced and subsequently recedes, which likewise contributes to afterflowing as has been observed. These phenomena are particularly pronounced and annoying when so-called double cartridges for two-component substances like glue, joint filler substances, dental impressions etc. are used with flow mixers connected to the cartridge opening since, because of the presence of the mixer, the outflow resistance and thus the internal cartridge pressure required for dispensing as well as the stress on the connection between attachment and cartridge are increased.
A primary task of the invention is to inhibit as much as possible the annoying and uncontrolled afterflow of a dispenser for cartridges after cessation of the plunger advance.